zephyr

History

Keith Packard 0b90fd5adf samples, tests, boards: Switch main return type from void to int As both C and C++ standards require applications running under an OS to return 'int', adapt that for Zephyr to align with those standard. This also eliminates errors when building with clang when not using -ffreestanding, and reduces the need for compiler flags to silence warnings for both clang and gcc. Most of these changes were automated using coccinelle with the following script: @@ @@ - void + int main(...) { ... - return; + return 0; ... } Approximately 40 files had to be edited by hand as coccinelle was unable to fix them. Signed-off-by: Keith Packard <keithp@keithp.com>		2023-04-14 07:49:41 +09:00
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src	samples, tests, boards: Switch main return type from void to int	2023-04-14 07:49:41 +09:00
CMakeLists.txt
prj.conf
README.rst
sample.yaml

README.rst

.. _syscall_perf:

Syscall performances
====================

The goal of this sample application is to measure the performance loss when a
user thread has to go through a system call compared to a supervisor thread that
calls the function directly.


Overview
********

This application creates a supervisor and a user thread.
Then both threads call k_current_get() which returns a reference to the
current thread. The user thread has to go through a system call.

Both threads are showing the number of core clock cycles and the number of
instructions executed while calling k_current_get().


Sample Output
*************

.. code-block:: console

    User thread:		   18012 cycles	     748 instructions
    Supervisor thread:	       7 cycles	       4 instructions
    User thread:		   20136 cycles	     748 instructions
    Supervisor thread:	       7 cycles	       4 instructions
    User thread:		   18014 cycles	     748 instructions
    Supervisor thread:	       7 cycles	       4 instructions